ALTER TABLE TO CURRENT Processing
During ALTER TABLE TO CURRENT processing, if the starting expression with the newly resolved DATE, CURRENT_DATE, or CURRENT_TIMESTAMP value does not fall on a partition boundary, the system must scan all of the rows before repartitioning the rows based on the new partitioning expression. Column partitioned tables must be empty before using ALTER TABLE TO CURRENT.
For an ALTER TABLE TO CURRENT operation where an all-row scan is unnecessary, the table can contain data.